Type I interferon regulates pDC maturation and Ly49Q expression.

Ly49Q is expressed on peripheral mouse plasmacytoid dendritic cells (pDC). Immature Ly49Q-negative pDC precursors acquire Ly49Q in the bone marrow and then migrate into the periphery. While searching for molecules that regulate pDC maturation, we found that type I interferon (IFN) inhibited Ly49Q acquisition in vitro. Infections that induce type I IFN production by cells other than pDC (a condition mimicked by poly(I:C) injection in vivo) increase the prevalence of Ly49Q(-) pDC in the bone marrow and peripheral lymphoid organs in wild-type but not IFN-alpha/beta receptor knockout BALB/c mice. Moreover, in vivo exposure to type I IFN causes some Ly49Q(-), but not Ly49Q(+), pDC to convert to conventional DC, defined as B220(-) CD11c(+) CD11b(+) cells. These data suggest that type I IFN regulates pDC development and affects their distribution in the body.